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authorT.J. Purtell <tj@mobisocial.us>2013-11-06 18:38:05 +0100
committerRussell King <rmk+kernel@arm.linux.org.uk>2013-11-07 00:19:06 +0000
commit6ecf830e5029598732e04067e325d946097519cb (patch)
treeb174b452cca9b7c9aa44a79cfa963b7c03539628 /arch/arm/kernel/signal.c
parente16b31bf47738f4498d7ce632e12d7d2a6a2492a (diff)
ARM: 7880/1: Clear the IT state independent of the Thumb-2 mode
The ARM architecture reference specifies that the IT state bits in the PSR must be all zeros in ARM mode or behavior is unspecified. On the Qualcomm Snapdragon S4/Krait architecture CPUs the processor continues to consider the IT state bits while in ARM mode. This makes it so that some instructions are skipped by the CPU. Signed-off-by: T.J. Purtell <tj@mobisocial.us> [rmk+kernel@arm.linux.org.uk: fixed whitespace formatting in patch] Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Diffstat (limited to 'arch/arm/kernel/signal.c')
-rw-r--r--arch/arm/kernel/signal.c14
1 files changed, 10 insertions, 4 deletions
diff --git a/arch/arm/kernel/signal.c b/arch/arm/kernel/signal.c
index ab3304225272..1aa5ecdd1b3d 100644
--- a/arch/arm/kernel/signal.c
+++ b/arch/arm/kernel/signal.c
@@ -375,12 +375,18 @@ setup_return(struct pt_regs *regs, struct ksignal *ksig,
*/
thumb = handler & 1;
- if (thumb) {
- cpsr |= PSR_T_BIT;
#if __LINUX_ARM_ARCH__ >= 7
- /* clear the If-Then Thumb-2 execution state */
- cpsr &= ~PSR_IT_MASK;
+ /*
+ * Clear the If-Then Thumb-2 execution state
+ * ARM spec requires this to be all 000s in ARM mode
+ * Snapdragon S4/Krait misbehaves on a Thumb=>ARM
+ * signal transition without this.
+ */
+ cpsr &= ~PSR_IT_MASK;
#endif
+
+ if (thumb) {
+ cpsr |= PSR_T_BIT;
} else
cpsr &= ~PSR_T_BIT;
}